Art of sealing quartz to metal



Aug. 24, 1965 Q, HElL ART OF SEALING QUARTZ TO METAL 3 Sheets-Sheet 1Original Filed Feb. 18, 1959 IN V EN TOR. OSKAR HE/L M W F ATTORNEYSAug. 24, 1965 Q. HEIL, 3,202,493

ART OF SEALING QUARTZ TO METAL Original Filed Feb. 18, 1959 3Sheets-Sheet 2 INVENTOR. OSKAR HE IL A TTORNEYS Aug. 24, 1965 o. HEILART OF SEALING QUARTZ T0 METAL 3 Sheets-Sheet 5 Original Filed Feb. 18,1959 INVENTOR OSKAR HEIL ATTORNEYS United States Patent Office 32%,493Patented Aug. 2%, 1%55 3,292,493 ART fil SEAHNG QUARTZ T0 METAL GslrarHeil, San Mateo, Calitl, assignor to Eitel-McCultough, inc, San Carlos,Calif., a corporation of icalifornia Original application Feb. 18, M59,Ser. No. 793,993, new Patent No. 3,'1l5,97, dated Dec. 31, 1963. Dividedand this application Dec. 26, 19%2, Ser. No. 247,145

8 :Clahns. (Cl. 65-43) This application is a division of my applicationSerial No. 93,993, filed February 18, 1959, now Patent 3,115,-

This invention relates to a seal structure and method by which quartzcan be joined to a metal member by a bond which is both vacuum-tight andphysically strong. As used herein throughout the description and claims,the term quartz means quartz in the vitreous, or non-crys talline state,often referred to as pure silica glass or fuse quartz.

Quartz is a very low loss dielectric with low dielectric constant and istherefore a very desirable substance for windows in high frequencyelectronic tubes such as klystrons linear accelerators. Quartz also hasvery high transparency for infrared and ultra-violet radiation, whichmakes it an excellent window for photo cells, lamps, and similar devicesin this frequency range. Some other outstanding properties of quartz areits extremely low thermal expansion coefficient, which results in greatthermal shock stability; its ability to withstand electron bombardmentand exposure to X-rays and other atomic radiation without receiving anyappreciable radiation damage; and its ability to withstand exposure tovery high electric field strengths b fore breakdown occurs.

in the past, only limited use has been made of quartz for the purposesdescribed, even though its desirable characteristics have been wellknown. The reason is that heretofore there has been no practical meansfor making a strong vacuum-tight seal between quartz and the metal partsof electronic tubes and other devices in which it is useful.

in recent years great strides have been taken in the art of making sealsbetween ceramic and metal, and ceramic is now used extensively as areplacement for glass in electronic tubes. The problem of making aquartz-tometal seal is much more severe than the problem of male ing aceramic-to-metal seal. The first difficulty results from the fact thatquartz cannot withstand the high to atures to which ceramic is subjectedfor substantial time during metalizing. As a matter of fact, quartzcannot be subjected to much over 1000" C. for any appreciable length oftime although it can withstand higher temperatures for very shortperiods. The effect of heating quartz over 1000 C. for appreciable timeis that recrystallization of the quartz takes place, resulting ininternal stresses which cause the quartz to crack. Accordingly, quartzcannot be metaiized by the same techniques which are used in metalizingceramic. In the case of ceramic the metalizing is accomplished bypainting or otherwise coating the ceramic with a mixture or" poweredmetal particles suspended in a suitable lacquer, and then sintering thecoating at temperatures of around 1400 C. for periods of around thirtyminutes. It will be appreciated that this metalizing method fails withquartz because of the high temperature and time periods required.

According to this invention the problems related to the temperaturelimitations of quartz have been solved by the discovery that it ametallic substance is applied to the quartz in sufhciently smallparticle size and with a sufficiently high degree of compactness thatthe mctalizing material can be sintered to the quartz at substantiallylower temperatures than are required in connection with the particlesizes and compactness associated with the metalizing methods used inconnection with ceramic. Thus, one feature of the invention is that thesubstance with which the quartz is metalized is applied in extremelysmall particles such as in the form of atoms or molecules. When themetalizing substance is applied in this manner it is possible to sinterit to the quartz under heat and time conditions which do not cause thequartz to rccrystallize.

Another reason why quartz is more diiiicult to metalize than ceramic isthat the thermal coefiicient of expansion of quartz is much less thanthat of ceramic. Ceramic of the type normally used in electronic tubeshas a coefficient of expansion of about 60x 10 while that of quartz isonly 6 10 In fact, the expansion coefficient of quartz is so low that itcannot be matched by any metal or for that matter by any othersubstance. Thus, even after solving the problem of low temperaturesintering the problem of expansion coefficient remains. As a result or"the extremely low coefficient of expansion of quartz, any metalizingmaterial which will form a strong bond to the quartz will tend to crackthe quartz as it expands and contracts relative to the quartz underthermal shock. Closely related to the problem presented by the lowcoefilcient of expansion of quartz is the ductility of the metal usedfor metalizing. Metalizing made of a non-ductile metal will exert moredestructive force on the quartz under thermal shock than a ductile metaleven though the coefficient of expansion of the non-ductile metal may becloser to that of quartz.

All of the metals which have been found by the application of thisinvention to achieve a strong vacuum-tight bond with quartz are metalswhich are non-ductile, that is, have high annealing temperatures.Accordingly, when such metals are bonded to quartz in any appreciablethickness the discrepancies in the coefiicients of expansion will causethe metal to tear away from the quartz under the influence of thetemperature changes which are associated with the metalizing procedureand in many cases the temperature changes which are associated withoperation of the device in which quartz is used. However, it has beenfound according to the invention that if the metalizing material isapplied in an extremely thin layer it is too weak to overpower theceramic, that is, the metal is in effect given an artificial ductility.By depositing the metalizing substance in the form of atoms or moleculesit is possible to make the metalizing so thin that it will not be strongenough to crack the quartz and yet be of a uniform thickness such thatthe entire area to be metalized receives a coating to which a metalmember can be joined.

After the quartz has been metalized with an extremely thin metal layer,it is necessary to have some means for joining the metal-izing layer toa metal member of the evice in which the quartz is to be used. It hasbeen found according to the invention that the metalizing layer can bebonded to a relatively thick metal member without causing the quartz tocrack it the relatively thick metal member is one which is extremelyductile, that is, one which has an annealing temperature substantiallylower than the annealing temperature of the metalizing material.

Further, it has been found according to the invention that the bondbetween the metal member and the metalizing layer must not involve anysubstantial alloying of the metal-izing layer. There are two reasons Whythere must not be any substantial alloying of the metalizing layer. Onereason arises from the fact that the metalizing layer must be so thin;for example, a thickness of only 2000 angstroms has been found to giveexcellent results. Thus, no appreciable amount of the metalizing layercan be used in alloying without eating the metalizing away from thequartz and thus destroying the bond between the metalizing layer and thequartz. The other reason why there must be no substantial alloying ofthe metalizing layer is that in the case of some metals which aresuiiiciently ductile .to be used as the metal member, an alloy whichwill bond the metal member to the metalizing layer is substantially lessductile than the pure metal of the metal member. Thus, a non-ductileinterface is formed which is in effect the same as increasing thethickness of the non-ductile metalizing layer and results in cracking ofthe quartz.

' According to the invention two solutions have been found to theproblem of detrimental alloying of the metalizing layer. One solution isremake the metal member of a metal which will not alloy with themetalizing layer. Heretofore it has been thought that there was no wayto form a satisfactory bond directly between metals which do not alloy.However, contrary to expectations it has been found according to theinvention that a strong, permanent pressure seal can be formed betweensuch metals, for example, between molybdenum and gold.

' This pressure seal, as distinguished from a pressure/seal betweenmetals which alloy, does not form an alloy at the interface. The othersolution is to form a br-aze-type bond between the metal member and themetalizing layer wherein no substantial amount of the metalizingmaterial is used up in the brazing alloy, and the alloy is more ductilethan the metalizin g material.

The purpose of this invention is to bond quartz to metal with a sealwhich is vacuum-tight and physically strong.

Another object of the invention is to provide a method by which a layerof metal can be firmly bonded to quartz without heating the quartz to anextent which will cause recrystallization thereof.

A further object of the invention is to accomplish quartz metalizing bythe application of an extremely thin uniform metal coating. 7

Another object of the invention is to provide a quartzto-metal seal inwhich a metal member is attached to a metalizing layer on the quartz bymeans of a bond which does not involve any appreciable alloying of themetalizing layer.

The invention possesses other objects and features of advantage, some ofwhich, with the foregoing, will be set forth in the followingdescription of the invention. It is to be understood that the inventionis not limited to the disclosed species, as variant embodiments thereofare contemplated and may be adopted within the scope of the claims.

Referring to the drawings:

FIGURE 1 is aside view, mainly in section, showing a klystron embodyinga quartz-to-netal seal in accordance with the invention;

FIGURE 2 is an enlarged sectional View showing the details of one of thequartz-to-metal seals in FIGURE 1;

FIGURE 3 is a cross-sectional view including a schematic wiring diagramshowing apparatus for applying and sintering metalizing on quartz;

FIGURE 4 is a cross section along the line 44 of FIGURE 3;

FIGURE 5 is a cross-sectional view of another embodiment of apparatuswhich can be used for sintering met alizing on quartz;

FIGURE 6 is a cross-sectional view of another embodimerit ofapparatuswhich can be used for metalizing quartz;

FIGURE 7 is .an elevational view, partly in section, of apparatus whichcan be used to obtain a pressure seal in accordance with the invention;

FIGURE 8 is a cross-sectional view similar toFIG- URE 2 showing anotherembodiment of the quartz-tometal seal according to the invention; and

FlGURE 9 is an enlarged sectional view of a portion ofthe quartz membershown in FIGURE 7 and is similar embodiments of the invention.

. V 4 to FIGURE 2 but shows'another embodiment of the quartz-to-metalseal according to the invention.

Referring to the drawings in more detail, FlGURE 1 shows a klystron ofthe type described in detail in the patent to C. E. Murdock, No.2,824,289, dated February 18, 1958. The klystron comprises an electrongun ll which projects an electron beam through a number of diift'tubes12, 13 and 14 into a collector 15. The electron beam as it passesthrough the gaps between the drift tubes reacts with cavity resonators,as explained in detail in the aforementioned Patent No. 2,824,289. Thecavity resonators are made of evacuated portions 18 and externalportions (not shown). The evacuated portions 13 of thecavity'resona-tors are made of disk-shaped metal end walls 19 connectedby a cylindrical window 2%} of insulating material. In the past,cylindrical windows 2% have been madeof glass or ceramic. The Window2.4) according to the invention is made of quartz. The seal between thequartz windows 26 and the metal end walls 19 are indicated generally at22 in FIGURE 1.

FIGURE 2 is an enlarged view which represents a preferred embodiment ofthe quartz-to-metal seal. In FIGURE 2 an attempt has been made to give aphysical conception of the sealing structure obtained in accordance withthe invention. Clearly defined layers of metalizing material havingvisible thicknesses are shown. However, it should be understood thatFIGURE 2 is for the purpose of clarification and that many of thedimensions shown therein are extremely exaggerated. As shown in thepreferred embodiment of FIGURE 2, there is a layer of molybdenum 23bonded to quartz cylinder 29. The bond between the molybdenum and quartzis enhanced by an intermediate deposit of titanium 24. The molybdenumlayer is extremely thin, being on the order of 1,500 to 5,000 angstroms,and the deposit of titanium is even more minute, being in theneighborhood of only 36 to 50 augstroms. A layer 25 of gold is bonded tothe molybdenum layer 23. The thickness of the gold layer is not criticalbecause of its extreme ductility. As will be discussed furtherhereinafter, the titanium and gold are not absolutely necessary butareextremely desirable because they facilitate th making of a high yieldstrong vacuum-tight seal.

Attached to the gold layer 25 is a metal sealing ring 2b made of gold.The metal ring 26 is bonded to gold layer 25 by means of a pressureseal, as will be described in more detail hereinafter. The thickness ofring 26 is not critical but is preferably on the order of 6 thousandthsof an inch. Sealing ring 26 is brazed or otherwise bonded to a secondgold sealingfring 27, which is in turn brazed to the thick metal endwall 19, which is usually copper.

The arrangement thus far described provides a strong, vacuum-tight sealwhich can be subjected to repeated heat cycling without damage. Thearrangement can be strengthened where desired, particularly inconnection with large heavy structures, by the addition of a quartzbacking ring 36%, which is also provided with metal layers 23, 24, 25 ofmolybdenum, titanium and gold, respectively. The gold layer 25 ofbacking ring 30 is attached to sealing ring 26 by means of a pressureseal, and the surface of ring 36 which abuts the metal end wall 19 isnot metalized.

As has'been previously explained, one of the features of the inventionresides in the manner in which metalizing is applied to the quartz.FIGURES 3 and 4 disclose apparatus for metalizing quartz according toone of the Essentially, the apparatuscomprises a vacuum-tight container31 formed of metal and walls 32 and 33 connected by a cylindrical sidewall having a lower metal portion 34 and an upper window portion 35 oftransparent material such as glass. Sealing rings 36 are provided at thejoints between various walls of the container. A rotatable shaft 37 iscarried by the end wall 32 and is provided externally of the containerwith means (not shown) for rotating it during the metalizing process.The upper end of the shaft 3? U is provided with suitable means forsupporting quartz cylinder 29. For example, the upper end of shaft 37can have pivotally attached thereto three arms 38 which are notched toreceive the end of cylinder 29 and are biased upwardly by spring 3?toward the axis of the shaft.

As previously explained, the invention requires that metalizing bedeposited on the quartz in the form of extremely small particles. Thisis accomplished in the apparatus of FIGURE 3 by vaporizing or sublimingthe metalizing material and allowing it to condense on the quartz. Tothis end six insulating plugs 46? are mounted in end wall 33. The twoplugs 4-0 at the left of FIGURE 3 carry an inverted U-shaped tungstenwire 41. The bend of the wire 41 is positioned within the containeradjacent the end of cylinder 2% and carries a small head 42 i titanium.In addition, a short length of molybdenum wire 43 is wrapped around thebend in wire 41. In order to prevent the molybdenum wire 43 from runningtogether and heading on the wire 4-1 when the molybdenum is heated highenough to vaporize, it is desirable to place a short coil of tungstenwire (not shown) on the tungsten wire 41 along with the coil ofmolybdenum 43 so that the turns of the molybdenum coil alternate withthose of the tungsten coil.

A second U-shaped tungsten wire 45 passes through plugs 4% on the rightof FIGURE 3 and carries on its bend a coil of gold wire A heater coil4?; is positioned within cylinder 29 with its leads passing through thetwo plugs ill at the center of FIGURE 3. Suitable means are provided forpassing current through wires 41, 45 and 48. For example, the leads forheater coil 43 can be connected to a llO-volt A.C. source through anadjustable autotransiormer St and wires 31 and 4-5 can be connected to all-volt A.C. source through an auto transformer Sl, a fixed transformer52 and a switch 53. End plate 32 is connected by means of tubulation Sto a conventional vacuum system.

Describing the operation of the apparatus shown in FIGURES 3 and 4, thecylinder 26 to be metalized is placed in container 31 as shown in FIGURE3. In order to obtain metalization only on the end of cylinder theinside and outside of the cylinder are coated with a removableprotective substance such as Aquadac. The vacuum system (not shown) isturned on and container 31 is evacuated. Rotation of shaft 37 is startedand then current is passed through the heater 4%, utilizing theadjustable transformer 56 to bring the temperature of the quartzcylinder 2t} up to about 800 to 960 C. It should be remembered that thequartz must not be heated over 1000" C. for any appreciable length oftime. Next, the wire 4-1 is heated, and in order to accomplish this itwill be noted that switch S3 occupies the position shown in FIGURE 3.Transformer Si is adjusted so that the titanium bead 32 is heated to ahigh enough temperature to vaporize it. As previously stated, only avery minute deposit of the titanium is necessary, and a thick depositcould not be tolerated. A deposit of around to St) angstroms has beenfound to be satisfactory. Next, the transformer 51 is adjusted toincrease the current flow and raise the temperature of the molybdenumcoil 43 so that it vaporizes and condenses on the previously depositedtitanium layer.

After the molybdenum layer has been deposited, the transformer 56 isreadjusted to allow the quartz cylinder 20 to cool down to about 560 to600 C. After this has been accomplished, the switch 53 in FIGURE 3 ismoved to the right to connect wire to transformer 51 which is readjustedto heat the gold coil 46 to vaporize it. The main purpose in applyingthe gold layer 25 is to provide a protective coating on the molybdenumlayer 23 so that it is not necessary to provide special handling of themetalized quartz during further processing to prevent oxidation of themolybdenum layer.

Although the combination of metals thus far described is preferred,other metals of similar critical characteristics can be substituted. Forexample, the titanium primer layer can be replaced by chromium,zirconium, columbium, tantalum, or molybdenum disilicide. Similarly, themolybdenum can be replaced by tantalum, zirconium, columbium ortitanium. It should be understood that when the molybdenum is replacedby the listed substitutes, there is little or no need for a separateprimer layer. As a matter of fact, molybdenum as well as all of thelisted substitutes can be deposited directly on the quartz without aprimer layer. However, a higher yield of perfeet seals is found toresult from the use of a primer layer when molybdenum is used as themain layer. In addition, silver can be substituted for gold as theprotective layer or coating 25. However, if silver is used, the sealingring 26 must be silver or copper instead of gold because silver and goldform a non-ductile alloy.

FIGURE 5 shows another embodiment of apparatus for sintering themetalizing layer on the quartz member 2%. This apparatus comprises ametal container 53 having a permanently attached end ring 59 and aremovable end plate as separated therefrom by a sealing gasket till.Plate 6% carries a cylinder 62 or very thin reflective metal such asnickel, reinforced at top and bottom by thicker metal sleeves 63 and 64.A removable closure 66 fits in the top of container 58 and carries threelengths of wire 67 which support the previously metalized quartzcylinder 2%. Suitable tubulation 69 and 70 is provided in container 58and closure 66, respectively, and a communication port 71 is provided incylinder 62. Cylinder 62 serves as the -eater for the apparatus, andcurrent is conducted to the cylinder by leads 74 and 75.

In order to utilize the apparatus of FIGURE 5, a layer of molybdenum orone of the listed substitute metals is first deposited by means ofapparatus similar to that shown in FIGURE 3, except that it can besimplified by elimination of wires 45, 46, 43 and the associatedinsulators and circuitry. It will be understood that according to thisern bodiment the quartz is not heated by the coil 48 during depositionof the metalizing, and the metalizing is not coated with gold. After themetalizing has been deposited by the described modified apparatus ofFIGURE 3, the quartz member is placed in the apparatus of FIGURE 5 andheated to a temperature of about 1300 C. for about 3 minutes to sinterthe metalizing. It should be noted that this is about the maximum timeand temperaure combination which the quartz can withstand. It isnecessary to provide a protective atmosphere in container 5% throughoutthe heating operation, and this is accomplished by evacuating thecontainer or by circulating a gas such as hydrogen by means oftabulation 69 and 70.

Still another embodiment of metalizing apparatus is shown in FIGURE 6which comprises a container having metal end walls '78 and '79 and aside Wall 3t) of insulating material. Side wall 86 carries tribulation81 and 82 and is separated from end walls 78 and 79 by means of sealingrings 83. A metal post 85 carrying a circular disc 86 serves as asupport for the quartz cylinder 20 which is to be metalized. The upperend wall 73 is made of molybdenum or one of the mentioned substitutemetalizing materials.

The procedure for using the apparatus of FIGURE 6 is to employ theprocess known in the art as cathode sputtering to cause particles to beknocked oil? of end wall 78 and deposited on the end of quartz cylinderMB. In order to use the cathode sputtering principle with thisapparatus, a gas such as mercury or krypton is introduced into thecontainer by means of tubulation 8i and 552. End Wall '78 is connectedby means of lead 87 to an appropriate source of negative DC. voltage,for example, 300 to 1500 volts, and end wall 79 is connected by means oflead 88 to the positive side of the voltage source. This voltage causesthe gas to ionize and form a plasma. The positively charged particles inthe plasma bombard the end wall 78 knocking olI particles which depositon the quartz cylinder Ztl. Although not absolutely necessary, it is de(not shown) from the Aquadac to an appropriate DC.

power source. Metalizing applied by the apparatus of FIGURE 6 strikesthe end of the quartz with such force that no additional heating isnecessary to accomplish sintering. a

After the quartz cylinder 29 has been metalized by one of the methodsand apparatus thus far described, it is necessary to attach a metalsealing ring to the metalizing. The preferred means of attaching thesealing ring is by a pressure seal. Apparatus for accomplishing thepressure seal is shown in FIGURE 7 and comprises a base plate 99 whichcarries a conventional hydraulic ram having a cylinder 91 and a pistonrod. 92. The usual hydraulic lines )3 and 94 are connected to cylinder91. The upper end of piston rod 92 carries a clamping head 95 on whichthe metalized quartz cylinder 26 is placed. A second clamping head asrests on top of the quartz cylinder 20 and has pivotally attached to theunder side thereof three tension rods 97 which have enlarged heads 93.Clamping head 95 is provided with three holes 95 which accommodate rods97 and are sufiiciently large to permit passage of heads 98. Base plate99 has three radial slots 99 in which the rods 97 are removablyreceived. A removable oven 1% surrounds the cylinder 2% and comprises aninverted metal cup iiii surrounded by a heating coil 102 and insulatingmaterial 103. Suitable inlet and exhaust tubes 1% and 105 are connectedto cup 191.

As previously mentioned in connection with FIGURE 2, the sealing rings26 are preferably made of gold. In order to make a pressure seal betweenthe gold sealing rings and the metalized quartz cylinder 20, the heatingcoil 162 is energized to bring the quartz cylinder 20 to about 600 to800 C., and then the hydraulic ram is operated to force piston rod g2and clamping head 95 up wardly. Clamping head 96 is held stationary bytension rods 7, and as a result both the sealing rings 26 are pressedagainst the metalized ends 'of cylinder 20. A pressure of around 2900psi. exerted forabout 10 min-' utes has been found satisfactory. Itshould be understood that other combinations of time, temperature andpressure will work. 'For example, if the pressure is increased, the timecan be decreased;

It will be recalled that the preferred metalizing arrange ment includesa final coating of gold and when this is done it is not necessary toprovide a protective atmosphere in oven 1%. When the metalizing does notinclude the final coating of gold, a protective atmosphere such ashydrogen is maintained in the oven by means of tubes 104 and 105. Afterthe pressure seal has been made, the oven 10% is lifted off and thehydraulic ram is vented to remove the pressure from the piston rod 92.Then rods 97 are moved radially outward so that heads 98 are removedfrom base.

' from the inner and outer cylindrical surfaces.

certain that no. appreciable amount of metalizing material is used inalloy with the nickel. Next, a silver or copper-silver brazing ring isplace against the nickel coating, and a sealing ring 26' made of copperis pressed against the brazing ring. Finally, the seal is heated tobrazing temperature to form an alloy Hi8. If desired, the nickel can beplated with silver instead of using a separate brazing ring. In anyevent, the brazing material should be no thicker than necessary to forma satisfactory bond because the thicker the brazing material is, thethicker will be the alloy layer, which is less ductile than the puremetal of sealing ring 26'. It should be understood that the silver andcopper substantially do not alloy with the molybdenum, and thereforethere is no danger of using up the metalizing in alloy. The fact thatsilver and copper do not alloy with molybdenum is the reason why thenickel coating is used, and as previously mentioned, the nickel coatingis so thin that it cannot take an appreciable amount of molybdenum intoalloy. If it were desirable to use a silver sealing ring,

then copper would he used as the brazing material.

FIGURE 9 is an enlarged 'view of a portion of a quartz 7 cylinder 26showing the simplest version of a seal made in accordance with theinvention. In FIGURE 9 the metalizing material consists entirely of asingle layer 23 or molybdenum or one of the listed substitute metals towhich a sealing ring 26 of gold, silver or copper has been pressuresealed in the apparatus of FIGURE 7.

As stated previously, the coefficient of expansion of metals is muchgreater than quartz. Therefore, if a quartz-to-rnetal seal is placed ina pol aroid stress analyzer, lines of stress are observed in the quartzcaused by the uneven thermal expansion, even though a high ductile metalis used. This stress is not large, and under ordinary conditions willnot be objectionable.

lt'was observed in the same analyzer that the thermal stresses are lessif the ends of the quartz tube, which are to be sealed to the metal, areslightly double-chamfered or beveled tofornr-a slight ridge disposedcentrally The amount of bevel to beused depends on the size of thequartz to be sealed and is readily determined by one skilled in the art.The angle of the bevel is usually between one and two degrees.

I claim:

1. A method of making a quartz-to-me'tal seal wherein the metal memberhas a coeflicient of thermal expansion greater than the quartz membercomprising the steps of depositing on the quartz a coating of a metalselected from the group consisting of'molybdenum, tantalum, zirconium,titanium and columbium, said metal being in the form of discreteparticles no larger than molecules the quartz to a crystalline form, andthen bonding to .7 said coating a member made of metal which will notplate 90. 'Then clamping head 96, is lifted, pulling rods 97 throughholes 95' and out of cylinder 20 so that the cylinder can be removed.

lthough a pressure type seal is preferred for attaching the sealing ringZdto the metalized quartz, a braze type seal of more limitedcapabilities can be made if certain precautions are taken. Inparticular, it is necessary that no substantial amount of the metalizingmaterial'is used up in the-brazing alloy and that the brazing alloy issub-- stantially more ductile than the metalizing material. For example,a satisfactory braze type seal, as shown in FIG- URE 8, can be made bycoating the layer 23 of molyb substantial thickness of non-ductilematerial and to make alloy with the metal of said coating, thelast-mentioned bonding being accomplished by the application of pressureat .a temperature below the melting temperature of both the metal ofsaid coating and the metal of said metal member;

' 2. A method of making a quartz-to-metal seal comprising the steps ofdepositing on said quartz a primer coating of a first substance selectedfrom the group consisting Will'sinter the coatings without transformingthe quartz to crystalline form to produce a metalized surface on thequartzthatisadapted to be hermetically sealed to a metal member having acoefficient of thermal expansion greater than the quartz.

3. A method of making a quartz-tdmet-al seal comprising the steps ofdepositing on said quartz a primer coating of titanium, depositing onsaid primer coating a main coating of molybdenum, said titanium andmolybdenum being in the form of discrete particles no larger thanmolecules at the time of arrival at the surface to be metalized, andheating said coatings at a temperature and time combination which willsinter the coatings without transforming the quartz to a crystallineform to produce a metalized surface on the quartz that is adapted to hehermetically sealed to a metal member having a coerhcient of thermalexpansion greater than the quartz.

4. A method of making a quartz-to-metal seal wherein the metal memberhas a coetlicient of thermal expansion greater than the quartz membercomprising the steps of placing a quartz member in an evacuated chamber,heating a supply of molybdenum in said chamber adjacent said quartzmember to a temperature at least high enough to cause the molybdenum tosublime and coat the quartz member, heating said molybdenum coating inthe chamber at a time and temperature combination which will sinter thecoating without transforming the quartz to a crystalline form, thendepositing a coating of gold on said molybdenum, the gold beingdeposited on the molybdenum-coated quartz while in said chamber, saidI110- lybdenum and said gold being in the form of discrete particles nolarger than molecules at the time of arrival at the surface to 'becoated, sintering the gold at a lower temperature than that at which themolybdenum was sintered, removing the quartz from the chamber, and thenbonding on the quartz a member made of a metal selected from the groupconsisting of gold, copper and silver, the last-mentioned bonding beingaccomplished by the application of pressure at a temperature below themelting temperature of the metal of which said member is made.

5. A method of making a quartz-to-metal seal comprising the steps ofplacing the quartz in an evacuated chamber, heating a supply of metal inthe chamber to a temperature at least high enough to cause the metal tosublimate and deposit on the quartz, and maintaining the temperature ofthe quartz during deposition at a temperature between 800 C. and 1000 C.to produce a metalized surface on said quartz to which a metal memberhaving a thermal coefiicient of expansion greater than said quartz maybe brazed.

6. A method of making a quartz-to-metal seal wherein the metal memberhas a coefiicient of thermal expansion greater than said quartz membercomprising the steps of placing the quartz in an evacuated chamber,heating a supply of titanium in the chamber to a temperature at leasthigh enough to sublimate and deposit on the quartz, then heating asupply of molybdenum in the chamber to a temperature at least highenough to sublimate and deposit on the quartz, the thickness of thetitanium deposit being less than that of the molybdenum, maintaining thetemperature of the quartz during deposition of the titanium andmolybdenum at a temperature between about 800 C. and about 1000 (3.,reducing the temperature of the quartz to between about 500 C. and 600C., heating a supply of gold in the chamber to a temperature at leasthigh enough to sub-limate and deposit on the molybdenum coating,removing the quartz from the chamber, and then bonding a gold member tothe gold coating by the application of pressure at a temperature belowthe melting temperature of gold.

7. A method of making a seal between a non-metal member and a metalmember where the metal member has a coefficient of thermal expansiongreater than the non-metal member comprising the steps of coating saidnon-metal member with a metalizing layer deposited in the form ofdiscrete particles no larger than molecules at the time of arrival atthe non-metal surface, heating said layer at a temperature and timecombination which will sinter the layer without causing a detrimentalchange in the non-metal member, and then attaching a metal member tosaid metalizing layer by means of a bond in which there is substantiallyno alloying of the metalizing layer.

8. A method of making a quartz-'to-metal seal wherein the metal memberhas a coeflicient of thermal expansion greater than the quartz membercomprising the steps of depositing on said quartz a metalizing layercomprising primarily a metal selected from the group consisting ofmolybdenum, tantalum, zirconium, titanium and columbium, said metalbeing no larger than molecular at the time of arrival at the quartzsurface, heating said layer at a temperature and time combination whichwill sinter the metalizing layer Without transforming the quartz to acrystalline form, and then attaching to said inetalizing layer a metalmember by means or" a bond in which there is substantially no alloyingof the metallizing layer.

References Cited by the Examiner UNITED STATES PATENTS 1,843,792 2/32Thomson -33 X 2,670,572 3/ 54' Smith 65-43 2,836,935 6/58 Stanworth etal. 65-43 X 3,015,013 12/61 Laszlo 11793.3 X 3,029,559 4/ 62 Treptow6543 3,053,698 9/62 Ogle et al. 117-107 X 3,063,871 11/62 Barkerneyer etal. 1l7-107 X DONALL H. SYLVESTER, Primary Examiner.

1. A METHOD OF MAKING A QUARTZ-TO-METAL SEAL WHEREIN THE METAL MEMBERHAS A COEFFICIENT OF THERMAL EXPANSION GREATER THAN THE QUARTZ MEMBERCOMPRISING THE STEPS OF DEPOSITING ON THE QUARTZ A COATING OF A METALSELECTED FROM THE GROUP CONSISTING OF MOLYBDENUM, TANTALUM, ZIRCONIUM,TITANIUM AND COLUMBIUM, SAID METAL BEING IN THE FORM OF DISCRETEPARTICLES NO LORGER THAN MOLECULES AT THE TIME OF ARRIVAL AT THE SURFACEBEING METALIZED, HEATING SAID COATING AT A TEMPERATURE AND TIMECOMBINATION WHICH WILL SINTER THE COATING WITHOUT TRANSFORMING THEQUARTZ TO A CRYSTALLINE FORM, AND THEN BONDING TO SAID COATING A MEMBERMADE OF METAL WHICH WILL NOT ALLOY WITH THE METAL OF SAID COATING, THELAST-MENTIONED BONDING BEING ACCOMPLISHED BY THE APPLICATION OF PRESSUREAT A TEMPERATURE BELOW THE MELTING TEMPERATURE OF BOTH THE METAL OF SAIDCOATING AND THE METAL OF SAID METAL MEMBER.